Four of five Macaca nemestrina that were infected with HIV-2287 and treated with d4T (Stavudine) remain in good health 3 1/2 years after drug therapy was discontinued (in July 1997), despite persistent virus infection. The results of in vitro tests suggest that the CD8+ cell population has a role in maintaining the low levels of circulating virus and the normal CD4+ cell numbers in the peripheral blood. One macaque did develop depletion of the CD4+ cell population and was euthanatized. The remaining macaques will continue to be monitored for clinical status and progression to disease. Two macaques are assigned to this project as normal controls. FUNDING NIH grant RR00166.